In the related art, there is a known method of observing a disease site in the pericardial cavity by inserting an endoscope thereinto from below the xiphoid process without performing thoracotomy (for example, see Patent Literature 1). At a distal-end surface of the endoscope, optical members for observing the interior of the pericardial cavity, such as an illumination lens and an objective lens, are disposed. Because the gap between the pericardium and the heart is small, in the case in which the method of Patent Literature 1 is used, the pericardium sags down in the area in front of the optical members of the endoscope, thus making it difficult to observe the interior of the pericardial cavity.
Therefore, in order to ensure a sufficient space for observing the interior of the pericardial cavity, an endoscope system provided, on the upper side of the endoscope, with a hood that protrudes farther forward than the distal-end surface of the endoscope has been proposed (for example, see Patent Literature 2). By lifting up the pericardium in a direction in which the pericardium is separated from the heart by using the hood, it is possible to ensure a sufficient space in the area in front of the distal-end surface of the endoscope, and thus, it is possible to perform bird's-eye-view observation of the heart by means of the endoscope. In order to realize less invasive surgery, it is preferable that the hood be a member that is smaller than the optical members of the endoscope, such as a guide wire.